Cochlear implant recipients have traditionally performed poorly on measures of speech intelligibility in the presence of noise. Recently, listeners incorporating both electric and low-frequency acoustic stimulation of the same cochlea have demonstrated significant improvements in speech perception in noise that exceed the sum of the intelligibility scores of acoustic and electric stimulation, alone. Thus, the main purpose of this study is to assess whether low-frequency acoustic processing, including frequency resolution, temporal resolution, and cochlear compression, can help account for the synergistic effect of combined electric and acoustic stimulation. Additionally, a subset of these listeners will be examined both pre- and post-implant to investigate the effects of the partially implanted electrode array on tow-frequency acoustic processing including low-frequency quiet thresholds in relatively small, discrete frequency steps, cochlear compression, temporal resolution, frequency resolution, and estimates of speech perception both in quiet and in noise. Both pre- and post-implant measures will be required to accurately assess the effects of the surgery on the apical end of the cochlea.